In RF design when antennas are used it is said that the antennas require a larger ground reference.If they have suggested a ground reference and if we are using a smaller one than recommended will it effect the performance so badly?

Also while we are designing if we have a GPS antenna which requires a 50*50 mm ground plane and a 4G antenna which also obviously require a large ground plane, can we do such that we can share the ground plane for both the antenna? will it affect the performance?

we are pouring ground plane on the top layer and also on the layer beneath it so is it enough ?

we cant increase the board size much since it is also a constraint

  • \$\begingroup\$ Please use line breaks and proper capitalzation. Not even going to try to decode that mess. \$\endgroup\$ – JRE Nov 10 '17 at 15:20
  • \$\begingroup\$ please have the decency to post a title without typing errors \$\endgroup\$ – jsotola Nov 11 '17 at 4:51

Yes, a smaller ground plane will affect your performance. By how much, you will have to measure and compare to the theoretical numbers.

Yes, they can share the ground plane.

Your ground plane should be solid (have no other traces), if possible.

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  • \$\begingroup\$ ok. Also since we are using a 4G antenna and GPS antenna, It is suggested that 18 Db isolation is to be achieved between GSM and GPS. Since our 4G antenna is linearly polarized and GPS is circularly polarized, Is the change in polarization enough to achieve high isolation.. \$\endgroup\$ – Vishak Nov 13 '17 at 4:31
  • \$\begingroup\$ Also by Friis Formula the separation between the two antennas to provide 20 DB isolation was calculated to be 100mm, But our board size is is restricted to <70 mm. So can the isolation be achieved by any other way? \$\endgroup\$ – Vishak Nov 13 '17 at 4:34

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